1. A line or tracing denoting varying values of commodities, temperatures, urinary output, etc.; more generally, any geometric or pictorial representation of measurements that might otherwise be expressed in tabular form.
2. Visual display of the relationship between two variables, in which the values of one are plotted on the horizontal axis, the values of the other on the vertical axis; three-dimensional graphs that show relationships between three variables can be depicted and comprehended visually in two dimensions.